Not Applicable
1. Field of the Invention
This invention relates to the field of light polarizers, and more particularly, to a reflecting light polarizer that passes light waves of a specific polarity while reflecting others.
2. Description of Related Art
There are two types of light polarizers typically used for providing polarized light. The first type of light polarizer is an absorbing light polarizer, which passes a portion of light having a specific polarization while absorbing the remaining light. The energy of the absorbed light is generally converted into heat energy. In systems requiring high light concentration, such as in liquid crystal display (LCD) and liquid crystal on silicon (LCOS) illumination systems, the heat load generated in each absorbing light polarizer can be greater than the than the amount of heat the light polarizers can efficiently dissipate. Thus, typical absorbing light polarizers are susceptible to damage caused by overheating when they are used in LCD or LCOS illumination systems. Furthermore, the light energy converted into heat energy becomes unusable for the intended purpose of providing illumination, and is thus wasted. Hence, absorbing light polarizers are not well suited for use in LCD and LCOS illumination systems.
A reflecting light polarizer is a type of light polarizer that passes a specific light polarity while reflecting the remaining light. One example of a reflecting light polarizer is a polarizing cube beamsplitter, which divides unpolarized light into P and S polarizations. However, a cube beamsplitter is expensive and bulky, and thus is not practical for use in small imager applications where price, available space and weight are issues.
Another example of a reflecting light polarizer is disclosed in U.S. Pat. No. 6,122,103 to Perkins et al. entitled Broadband Wire Grid Polarizer for the Visible Spectrum (hereinafter xe2x80x9cPerkinsxe2x80x9d). Perkins discloses a broadband wire grid polarizer for the visible spectrum that has a plurality of elongated elements supported on a substrate. Ribs formed by etching slots extend from a substrate and support the elements, which are relatively long and thin. The dimensions of the elements are critical, and thus the manufacturing process for the broadband wire grid polarizer can be complicated. Accordingly, broadband wire grid polarizers are relatively expensive. Hence, what is needed is a reflecting light polarizer that has reduced heat loss and improved light energy efficiency in comparison to absorbing light polarizers, yet is small, light, and inexpensive to manufacture.
The present invention is a reflecting light polarizer having improved polarizing efficiency, and a method of manufacturing the reflecting light polarizer. The reflecting light poplarizer includes a first non-linear mating surface, a second non-linear mating surface and a polarizing coating disposed between the first nonlinear mating surface and the second non-linear mating surface wherein a first light polarization is transmitted through the reflecting light polarizer and a second light polarization is reflected by the reflecting light polarizer. It should be understood within the context of this application that xe2x80x9cnon-linearxe2x80x9d refers to a surface that is not flat or that is jagged such as a saw tooth structure. The reflecting light polarizer can further include glue disposed between the first non-linear mating surface and the second non-linear mating surface. The reflecting light polarizer also can include at least one clamping device securing together the first non-linear mating surface and the second non-linear mating surface. Further, the first and second mating surfaces can have substantially continuous contact with the polarizing coating disposed between the first and second mating surfaces. The first and second non-linear mating surfaces can include at least one planar segment and the cross section of at least one of the first and second non-linear mating surfaces can be saw tooth shaped. The first and second non-linear mating surfaces can be glass, plastic or crystalline.
In another embodiment, the reflecting light polarizer can include a first mating surface which includes a plurality of first planar segments and a plurality of second planar segments, the second planar segments being interposed between adjacent ones of the first planar segments, a second mating surface which includes a plurality of third planar segments and a plurality of fourth planar segments, the fourth planar segments being interposed between adjacent ones of the third planar segments, a polarizing coating disposed between the first planar segments and the third planar segments, and a mirror coating disposed between the second planar segments and the fourth planar segments.
A method of manufacturing a reflecting light polarizer can include the steps of (a) depositing a first polarizing coating on at least one mating surface of a plurality of plates, (b) securing together the plurality of plates with the first polarizing coating disposed between the mating surfaces of adjacent plates, (c) cutting the secured plurality of plates along at least one first cross section to form a plurality of plate sections, each of the plate sections having at least one cross sectional surface, (d) applying a second polarizing coating to a plurality of the cross sectional surfaces, (e) securing together the plurality of plate sections, wherein the cross sectional surfaces of adjacent plate sections are mated together and the polarizing coating is disposed between the cross sectional surfaces being mated, and (f) cutting the plurality of plate sections along at least one second cross section.
The first cross section is substantially perpendicular to the at least one mating surface and the second cross section can be disposed approximately 45 degrees with reference to the first cross section. Further, the first polarizing coating and the second polarizing coating can be a common polarizing material. The plurality of plates can be secured together with glue. The plurality of plates also can be secured together with a clamping device.
Another method manufacturing a reflecting light polarizer can include the steps of (a) molding or extruding a first plate having a first mating surface, (b) molding or extruding a second plate having a second mating surface, (c) depositing a polarizing coating to at least one of the first mating surface and the second mating surface and (d) securing the first mating surface to the second mating surface. Glue can be disposed between the first mating surface and the second mating surface. At least one clamping device can secure together the first mating surface and the second mating surface.